[Phys-L] physics in the real world : WAN in a cage
[Bernard wrote, in part.....
-
- bernard cleyet via Phys-l
<phys-l@mail.phys-l.org>UnsubscribeTo:phys-l@phys-l.orgCc:bernard cleyet,Linda
BenetTue, Oct 3 at 7:52 PM/snip/
-
- My reasoning grid spacing, so I’ve read, one tenth of wave length is good
enough. My experience is about half wavelength makes equivalent of half
silvered (Al of course) for interferometer splitter. [1] Since no geo. hammer
or ruler supplied in pic. ...
/snip/
_______________________________________________-
About scaling John's images: security cages (in this country at least) are
often on 2 inch (50 mm) centers. This accords with the Lexmark printer size.
A Lexmark CS735 dc which looks similar has a footprint of 479 X 489 mm (18.9" X
19.25").A signal at 600 MHz has wavelength 12.5 cm and at 800 MHz it is 9.4 cm.
Using Bernard's assertion that a 1/10 wavelength wire cage is impermeable to
radio signals at that frequency or lower implies a high attenuation to signals
at 10 X 50 mm or 50 cm lambda (600 MHz)Bernard's ratio for 3dB attenuation is
for signals of 2 X 50 mm or 10 cm lambda ( 3 GHz)
This supports John's finding that a two inch wire spacing cage would provide
considerable attenuation.I like Bernard's method of checking attenuation
practically, though it took a little searching to find that covering a metal
trash can with an M2 implies a metal skin laptop like the Macintosh.